Recruiting drivers from competitors isn't necessarily a bad thing. It's the tactics used here to attempt to kill Lyft by making it bleed cash that are unethical.
"Earlier this month, CNN reported that Uber employees around the country ordered and then canceled 5,560 Lyft rides, according to an analysis by Lyft. (Lyft arrived at this figure by cross-referencing the phone numbers of users who tried to recruit Lyft drivers to Uber with users who had previously canceled rides.) "
The amount of money involved in the cancelled rides is inconsequential to Lyft's success. 5,000 cancelled rides is what, about $100,000? Techcrunch reported a $100 million annual gross revenue rate at Lyft last December, with 6% weekly growth.